The phenomenon of physical hardening and an assessment of its influence on the properties of of asphalt materials is presented based on a review and critical assessment of available literature on this topic. Background information is presented on this reversible property known as physical aging in non-asphalt materials such as polymers. The influence of physical hardening on asphalt binders is explained. Studies exploring physical hardening in asphalt mixtures are reviewed. The complex subject of the influence of physical hardening on pavement cracking performance is covered based on a review and assessment of the literature on this subject.
The selection of asphalt binder content is a key parameter for successful performance to resist both rutting and cracking. In the earliest time, binder content was selected visually. Marshall mixture design, developed in the 1940s, instituted the use of volumetric calculations. Initially the design method was based on total asphaltic content and did not consider that some of the asphalt binder was absorbed into the aggregate. In 1962 the Asphalt Institute added Voids in the Mineral Aggregate as a design criterion that set the design asphalt binder content based on an effective volume of asphalt on the outside of the aggregate plus the amount of asphalt binder absorbed in to the aggregate. The Marshall volumetric calculations were adopted into the Superpave method of design. Recently, interest in the cracking behaviour of asphalt mixtures has been increasing. Associated with this interest is the determination of how much effective asphalt binder content is in a mixture. This paper discusses the setting of asphalt binder content for mixtures, the relationship of asphalt binder parameters, and a method that can independently evaluate asphalt binder content. The role of aggregate specific gravity in volumetric calculations is highlighted. The method to evaluate asphalt binder content can be used during the mix design phase, as well as the construction and mixture acceptance process.
Project management is a fundamental part of what Stantec offers in its engineering, design and planning work for the transportation sector, as well as other sectors around the world. If Stantec’s Quality Management System is the brain that analyzes and provides feedback on our performance in project management, our 10-Point Project Management Framework is the heart that keeps it alive and allows it to thrive. Stantec’s Quality Management System was introduced in response to a need for measurable protocols in project management and control across the company. At its core, the Quality Management System includes our 10-Point Project Management (PM) Framework, which guides the development of our projects from start to finish. A key component of the PM Framework is the PM Boot Camp, a full-day in-class session delivered year-round in our offices around the world. The Boot Camps incorporate safety moments, group exercises, and specific examples dealing with real experiences in project management at Stantec. The Boot Camps have been delivered at over 340 sessions in 135 office visits, and train over 700 of our PMs and project support people annually. Since the launch of the Boot Camps, over 3,800 Stantec PMs, leaders and support staff have taken the training, representing over 48,000 person hours of face-to-face learning. Our PMs have consistently rated their satisfaction with the training at 90-92%. The connection of the PM Framework to practical situations, as well as the knowledge and experiences of their peers, confirms the value of the training to our PMs as well as senior leadership.
Metrolinx, a Government of Ontario Agency, is currently undertaking construction for the Eglinton Crosstown Light Rail Transit (ECLRT) project which is, in total, 19 km long, 10 km of which are constructed in tunnels. Eglinton Avenue, a major arterial road in Toronto, accommodates four (4) lanes of traffic. The area has been developed approximately 100 years ago. The ECLRT tunnels run primarily under the Eglinton Avenue Right of Way (RoW) and are passing under significant existing infrastructure including trunk brick sewers which have been deemed to be at risk of failure due to losing ring compression as a result of ground settlement due to the tunneling operations. As a precaution, to mitigate the risk of catastrophic failure, these brick sewers were lined using Cured in Place Pipe (CIPP). One tunneled section passes directly under the Fairfield Combined Trunk Sewer (CTS) – a 1200 mm (48 inch) diameter brick sewer consisting of two or three ring brick cross sections (depending on depth), likely constructed in a hand mined tunnel. The undermined section of the sewer varies in depth from ~7 m to near ~21 m (to invert). A jet grouted station headwall had to be constructed in the upper reaches of the sewer, creating a sub-section where differential settlement would occur. It was therefore anticipated that the Fairfield CTS would likely loose compressive ring forces and collapse catastrophically. The City of Toronto (the City) requires CIPP liners to be designed to the “Fully Deteriorated State”, meaning that the host pipe will not provide/contribute any structural support. The City had, due to the high risk impacts from failure (100’s of flooded basements), mandated that a Safety Factor of 3.0 be used for the design. The depth of the sewer, high water table and restrictions on the Structural Dimension Ratio of CIPP liners meant that the Safety Factor could not be achieved in the design using a single pass liner installation. Relining of combined sewers requires approval from the Ministry of the Environment and Climate Change (MOECC) to ensure that relining does not cause additional combined sewer overflows. The City’s model showed significant flows surcharging in the upper reaches of the sewer. An extended period of flow monitoring and calibration was required to confirm the existing and projected hydraulics to show how the sewer would perform following relining. The hydraulic capacity of the sewer was in the range of up to 2.3 m /s. Given the depth of the sewer of up to 20 m, bypass pumping the full capacity of the sewer was deemed not economically feasible; this would have required a long-term full closure of Eglinton Avenue and significant excavation to allow pumping access to the sewer. This paper summarizes how these challenges were addressed using an innovative way to minimize flooding and construction risks.
The City of Toronto, the largest municipality in both population and number of vehicles in Canada, does not currently have an official position or policy regarding automated and autonomous vehicles (AVs); however, that does not mean the City has been sitting idly by. The Transportation Services Division has been actively monitoring AV developments, and working with various stakeholders to improve understanding of what they could mean for all Divisions within the City of Toronto. This plan intends to lay the groundwork for moving ahead, without predetermining the answers. The plan's goals and objectives are based on a strategy of being as technologically agnostic as possible to improve services in a manner that benefits today, but also facilitates improvements for tomorrow. This plan will create a framework that will prepare Transportation Services to take a leadership role in understanding the potential implications of automation, guiding policy analysis, and identifying ways to expand safe mobility for all users.
This paper’s objective is to introduce a design approach which improves the performance and value of buried structures. This approach involves widening the design lens to more systematically consider sustainable and resilience aspects. Owners desire sustainable transportation networks which regenerate the environment, support society, and minimize financial cost. For a transportation network to be sustainable it needs to meet the needs of current and future generations in terms economic vitality, social equity, and a healthy environment (Transportation Research Board, 2017). A sustainable transportation network is resilient and can adapt or accommodate unexpected events with minimal disruption to society (Transportation Research Board, 2017). Transportation networks lacking resilience experience disruptions, resulting in large repair costs, negative costs to the economy from disrupted travel, and expose the public to safety hazards. Agencies need resiliency to address climate change impacts on transportation systems within the context of their available resources. Buried structures, commonly referred to as buried bridges, culverts, or soil-metal structures, are structures which derive their support from composite interaction between the structure and surrounding soil. Buried structures have spans up to 40 m and are found across Canada. Buried structures have several accelerated bridge construction benefits such as an ability to be rapidly constructed, and installed costs which are typically 33% to 67% lower than traditional beam bridges (AFS40, 2013).This paper will provide insight into where buried structures provide value compared to traditional beam bridges, and practical approaches which increase the likelihood of a buried structure design that: Is better able to withstand the test of time and unexpected events; Minimizes financial resources; Minimizes disruption and in some instances, regenerate society and the natural environment.
As Ontario’s highway network expands and is subjected to increasing traffic volumes, the Ministry of Transportation Ontario (MTO) is challenged to look for new and innovative solutions to preserve and maintain the highway system. The ministry has identified a few high truck traffic sections having Average Annual Daily Truck Traffic (AADTT) greater than 25,000 that are experiencing progressively early rutting failure, and a few thick asphalt pavements experiencing full depth cracking. To reduce impacts to the travelling public, these high volume highways require all major maintenance and rehabilitation works to be performed under tight nightly construction closures. The typical rehabilitation holding treatment of mill and overlay at these locations may last only 3 to 5 years, rather than the expected 8 to 12 years, before the rutting and cracking return. Based on the progressively shorter lifecycles of this holding strategy, the ministry is investigating a potentially more life cycle friendly option of using overnight precast concrete mill and inlay techniques to mitigate this progressive rutting and cracking challenge. This paper describes an MTO pilot project using precast concrete slabs to rehabilitate a deep strength flexible pavement. The paper discusses how three different slab support systems were evaluated based on factors such as load transfer and ease of construction; the challenges of construction staging based on an 8 hours work window, with adaptations of horizontal and longitudinal joint details for the anticipated temporary and permanent works; lessons learned and next steps. Furthermore, the paper presents post construction roughness, load transfer efficiency and friction results of the tined longitudinal texture on the precast slabs.
As it is well documented, structural behaviour of flexibles pavements in cold regions is significantly affected by environmental factors and traffic loads. When it comes to pavement damage, the action of freeze and thaw is one of the most important inputs to consider. During thaw, the loss of bearing capacity is addressed by the seasonal load restriction policies enforced in many countries. On the other hand, during winter, frost action induces an important increase in the bearing capacity of flexible pavements due to the viscoelastic response of asphalt concrete and to the freezing of pore water in granular materials and soils. The pavement strengthening with frost penetration has led some transportation agencies to allow winter weight premiums (WWP). Currently, the main issue related to WWP programs is the variety of legislation for both among and within jurisdictions. This variety is caused, in part, by the lack of a rational decision criterion for the application of an axle load limit increase based on the mechanical behavior of frozen pavements. The objective of this project was to document the mechanical behavior of freezing pavements and to develop a rational criterion for the onset of winter load premiums. An experimental approach with the use of Laval University full-scale heavy vehicle simulator was considered to monitor the response of two different flexible pavements built in a 24 m3 indoor test pit over a low plasticity clay and a silty sand subgrade soils, respectively. They were instrumented to monitor temperature profiles, surface deflection, as well as stress, strain and moisture content in each layer. The simulator was used to apply the air freezing temperature (-10 °C) and to periodically load the pavement surface using a standard dual-wheel set (half axle) varying in the range of 4500 to 6250 kg. The results collected allowed documenting how the response of different pavement structures changes with respect to frost penetration and temperature, and allowed quantifying the effect of the load magnitude on the change of the pavement response and damage.
The Traffic Monitoring Practices Guide for Canadian Provinces and Municipalities (Guide) provides the first national-level guidance on the planning, design, and implementation of traffic monitoring programs for Canadian provinces and municipalities. The primary objectives of the Guide are to promote uniformity in the approach and techniques used to deliver traffic monitoring programs in Canada and to improve the quality of the traffic data provided by these programs. The scope of the Guide encompasses all functions within a traffic monitoring program, namely: program design and evaluation, data collection, data analysis, and reporting traffic data. Separate guidance is provided for motorized and non-motorized modes. The Guide also addresses the unique issues and challenges associated with monitoring interrupted traffic flow conditions, which are common in urban environments. It is intended for use by transportation professionals involved in the planning, design, implementation, and management of traffic monitoring programs for provincial and municipal agencies in Canada. Professionals whose responsibilities involve the application of traffic data are also expected to benefit from this Guide.
One challenge facing transportation agencies employing Spring Weight Restrictions (SWR) is the ability to broadly monitor the road network for critical real time changes in road strength. Some agencies employ a subjective assessment of road roughness changes as a proxy to changes in strength and the need for further weight restrictions, though the geographic scope is limited to the travel of the road supervisor. Smartphone devices have been shown to be effective and accurate mobile platforms for collecting accelerometer data that can be converted into International Roughness Index (IRI) values. These devices have the potential to expand the extent and frequency of roughness monitoring over spring thaw if instrumented on fleet vehicles or crowd-sourced. This could support the development of objective trigger values for changes in roughness that would support the decision-making by a district engineer regarding imposing additional weight restrictions or focusing strength testing. If changes in roughness could be correlated with changes in strength, it may be possible to isolate specific areas of road weakness at high speed and in real-time. This research explored the potential of using smartphones to monitor road roughness changes on 1 km sections of two proximate collector and local highways over the SWR period in New Brunswick from March 15 – May 17, 2015. IRI values were calculated from an average taken from four runs on 26 different days at a speed of 80 km/h, reduced to 60 km/h on the local highway due to excessive road heaving. IRI values doubled from baseline to peak on both sections (collector and local baseline (peak): 1.35 m/km (2.54 m/km); 3.34 m/km,(6.60 m/km)) within the first two weeks of SWR, returning to baseline values two weeks before SWR ended. Data collection twice a week would capture the majority of significant changes in IRI values between observations. The change from a baseline IRI to the peak IRI and back occurred within the SWR window, suggesting the dates were appropriate if roughness was correlated with strength. Further work should explore trigger values that initiate a protocol to respond to drastic weather changes and the relationship between road strength and IRI.
The Plessis Road Widening and Grade Separation (Underpass) at CN Redditt Subdivision was considered a Short Term City of Winnipeg (COW) project. Short Term projects have the highest priority for funding and a key driver for this project was the funding contribution by the Building Canada Fund, which was established under the 2007 Federal budget for projects from 2007 to 2014. The COW awarded the preliminary and detailed design for the Plessis Road widening and grade separation at CN Redditt Subdivision in July 2012 to AECOM Canada Ltd. (AECOM) Construction on the first of five contracts began in summer 2013 and the project was substantially complete on October 3, 2016. Two lanes were opened to traffic in October of 2015 and all remaining lanes were open by September 2016. The final project upgraded Plessis Road from a two lane undivided, road at-grade crossing, to a four lane divided grade separated facility. The roadway services an industrial area, including truck traffic from CN’s intermodal facility located south of the project along Plessis Road. The many challenges for the project included dealing with multiple stakeholders, maintaining rail traffic throughout the duration of the project and meeting a very short design and construction schedule. Major stakeholders in the area consisted of an oil pipeline valve station located on the northeast corner of the project, oil pipelines north of the CN mainline, CN double mainline track, the CN Transcona Maintenance Shops/Yard lead, the Malteurop Plant lead, Manitoba Hydro, MTS and Shaw. Design challenges included providing clearance between the roadway surface and the underside of the rail bridge, which utilized through-plate-girders to achieve the minimal profile required, given that Dugald Road was located 300 m south of the tracks. A major land drainage channel for the COW, located on the south side of Dugald Road, could not be relocated without major cost implications and could not flow into the underpass area. The existing land drainage system was at capacity and the underpass runoff required storage prior to discharging into the existing system. The end result was the successful completion of the project using alternative solutions from numerous engineering disciplines, with minimal disruption to the stakeholders involved. The increased road and rail traffic experienced the day the first two lanes opened, has proven that the project was required to meet travel demand forecasts.
These days there is a lot of discussion about climate change and its impact on pavement infrastructure, including construction and performance. Green technologies, including alternative materials and recycling, and sustainable transportation also get a lot of attention. These subjects are important and the authors of this paper have written numerous papers on this. However, there is one subject that has somewhat became forgotten. This is pavement quality. It is expected that since production and paving technology is getting better, and there are advanced and innovative materials, the issue of pavement quality has been solved and does not need attention. However, the reality is just the opposite. There are alarming voices in a number of provinces and among municipalities that pavement quality has drastically decreased. It is common to hear that in the past, pavements lasted 20 years, and recently you are lucky if you get half of this, and there are examples of dramatic premature failures. Some of this may be due to excessive traffic loading or extreme climate, but these are rare cases. More frequently, the problem is that the quality is ignored and taken for granted. Pavement quality starts with pre-engineering, proper geotechnical investigation, analysis, design, appropriate specifications and quality construction. Reducing the geotechnical investigation to the bare minimum, or sometimes not doing it at all, is the first step to compromising quality. There is the same concern with pavement design, squeezing it to the minimum and assuming overly optimistic parameters. There are also numerous examples of implementing an inappropriate rehabilitation treatment. This is particularly a problem on alternative finance and procurement projects where there is less independent checking and testing. Substandard materials, inadequate design thickness and poor construction practice combine to increase risk of premature failure. Too often, Quality Assurance field and laboratory testing is reduced to the minimum or not required at all. This is particularly the case on projects where performance specifications are followed. On these projects, the contractors control themselves and QA testing is considered an unnecessary expense. But is it? Pavements that last half as long or less of what they should are very costly for tax payers. This paper includes examples of pavements where poor investigation, design and construction practice or the use of substandard materials were reflected in compromised performance. It also includes recommendations of how to address the problems based on the authors’ extensive experience in pavement and materials engineering.
The Urban Heat Island (UHI) phenomenon has been observed in hundreds of cities across the world, which have been shown to be warmer than adjacent rural areas. Within a city however, the heterogeneity and large number of variables acting simultaneously can make it difficult to understand how UHI develops at a microscale. Urban roads can have different materials and layered structures (collectively called ‘pavement geometry’) in a city and can also be positioned differently with respect to the urban form. A three-factorial analysis was performed using an uncoupled pavement-3D urban canyon model to investigate how pavement geometry, urban form, and meteorological conditions affect microscale UHI. Representative temperature data from Chicago, USA was obtained and the UHI in a simulated urban area was evaluated for the warmest and coldest hours of the year. During the warmest hour, urban form and pavement geometry could increase the microscale UHI by an additional 3 at distinct spatial locations. Whereas, during the coldest hour which included no sunlight, urban form played a more significant role to locally increasing the UHI by 1 to 1.5 . Additionally, in closed urban canyons with constricted wind flows, pavement geometry has a particularly important role to play, whereas in more open spaces, the wind flow pattern affects the UHI. Ultimately, multiple microscale UHI case studies are recommended for individual cities to factor in the large number of site-specific variables.
One of the most important elements in highway design is the sight distance available to road users. Sight distance is the visible distance required by a driver to complete a certain maneuver (e.g. coming to a complete stop). If the available sight distance is less than design requirements, the likelihood of a driver safely completing that maneuver decreases. Current methods of measuring sight distance are very difficult, labour intensive and time consuming. Existing methods to obtain sight distance information require field visits or graphic analysis of as-built drawings. This paper proposes an algorithm to automatically extract sight distance from Light Detection and Ranging (LiDAR) data by simulating observer and target points along the virtual highway. LiDAR data is first used to create a surface model of the road. Points representing observers and targets are then created along the highway of interest. ArcGIS software is then used to create lines between the observer-target pairs and obstructions blocking the sightlines are then detected in ArcGIS. A VBA algorithm is written to compute the available sight distance along each sightline. The proposed algorithm was tested on a segment on highway 36 in Alberta. The extracted information was compared to Alberta highway design guidelines and limitations were found to both stopping and passing sight distance on existing highways. It was found that minimum stopping and passing sight distance requirements were not met in two regions. In order to analyse the impacts of sight distance limitations on safety, collision records at limited sight distance locations were assessed. Fixed object collisions and animal collisions were common in those areas, indicating that sight distance limitation could have been a factor in collision occurrence. The method developed in this study could be extremely useful in timely assessment of sight distance on highways, which could, in turn, help address limitations before safety problems arise.
In pavement management system (PMS), the time to maintenance is generally estimated based on the predicted condition of the pavement. A deterministic approach is applied in the PMS to estimate the time to maintenance by following the deterioration equation of performance index. However, the probabilistic approach will further estimate the probability of failure over the estimated time to maintenance. For this reason, a probabilistic approach is applied in this study to estimate the probability of failure of pavement based on both overall condition and individual distress. In this approach, the probability of failure is estimated from the distribution of the mean time to maintenance. These mean time to failure or maintenance are calculated from the overall condition of pavement in terms of the pavement condition index (PCI) when the trigger value becomes 65 or less. However, the pavement may expect failure due to any specific distress (if the target value of failure is reached for any individual distress) before reaching the PCI trigger value of failure. For this reason, the probability of failure of each specific distress is also investigated along with the overall condition of the pavement.
Investing in an efficient transportation system is crucial to a country's economy. While federal and provincial governments in Canada have access to income and consumption taxes, municipal governments typically rely upon property taxes, fees, and transfers from senior levels of government to fund transportation infrastructure. With modern fuel-efficient cars, alternative energy sources, and advanced technologies used in vehicles, fuel tax, as currently administered, may become a less reliable source of funding. Municipalities face a desperate need to find stable, long-term funding for vital roadway projects in an environment of increasing demands from users, downloading of responsibilities, dwindling or unreliable transfers, and reluctance from senior government to grant additional taxation powers. Municipalities have begun examining alternative funding mechanisms including local improvement taxes, development charges, user fees, tax increment financing, public-private-partnerships, and Contribution in Aid of Construction (CIAC). Strathcona County has expanded on the CIAC concept for funding infrastructure to support industrial growth in an equitable manner that manages risk and adheres to Alberta`s Municipal Government Act. Contribution in aid of construction is a condition placed on the approval of subdivision or issuance of a development permit that requires developers to enter into a development agreement with the municipality to construct or pay for the construction of particular roadways that give access to the development. Strathcona County is a specialized municipality located immediately adjacent to Edmonton, Alberta. The adoption and usage of a CIAC policy within Strathcona County's oil and gas-based economic expansion zone, the Industrial Heartland Area (IHA), has proven to be an effective, flexible, equitable and simple means of upgrading and constructing the system of local roads that satisfies the needs of industrial developers without putting undue financial burdens on industry or County taxpayers. This paper discusses the advantages and disadvantages of many different alternative funding methods available to municipal government in Alberta; describes the experience Strathcona County has gained in implementing CIAC as a funding mechanism; and demonstrates how the CIAC system functions. Although it is recognized that no single method will work in all situations, in all communities, it is hoped that important lessons are conveyed through the example given.
Metrolinx conducted a stated preference survey on passenger sensitivity to transit fare, cost, and other service factors in the Greater Toronto Hamilton Area (GTHA). This project is the largest fare sensitivity survey conducted within the GTHA (3,500+ responses collected from September to October, 2016), and the first fare sensitivity study completed in the region in decades. The results include elasticities for various travel segments broken down by time of day, origin/destination, and mode of travel, enabling better forecasts of how specific groups of passengers (e.g., off-peak GO Rail users, automobile users, local transit users) might respond to changes in price and service. This work can help evaluate existing and future pricing strategies, service changes, and other projects that may affect revenue and ridership across the entire GTHA.
Life Cycle Cost Analysis (LCCA) is an engineering tool that is used to facilitate sound investment decision-making in the management of infrastructure. Transportation agencies can use LCCA in the selection of cost-effective pavement designs, and evaluation of future maintenance, rehabilitation, and/or reconstruction strategies. Using LCCA can also increase transparency in the project selection process, ensuring agencies make strategic decisions that maximize the expected value of their investments. This paper reviews the current LCCA practices in place across transportation agencies in Canada and in select international agencies. The review focuses on the LCCA policies of the provinces of Alberta, British Columbia, Manitoba, Nova Scotia, Ontario, Quebec, and Saskatchewan. The practice guidelines of the Federal Highway Administration (FHWA), American Concrete Pavement Association (ACPA), Asphalt Pavement Alliance (APA), and the World Bank (WB) are also reviewed. The objective of the study is to develop a Canadian LCCA Standard Practice Guideline based on best practices. The guideline provides guidance on LCCA for alternate pavement-type bidding. The guideline is also instrumental in the development of user-friendly excel based tool to aid in the analysis of life cycle costs of alternate pavement designs. The study reviewed best practices relating to length of analysis period, discount rate, (agency, user, and environmental) costs, economic criteria method, and computational approach for life cycle cost analysis. Based on the review, recommended practices for conducting LCCA in pavement design were identified and are proposed as input for a Standard Practice Guideline.
Metrolinx is developing an evidence-based evaluation framework for business cases to inform investment decisions for transit projects. The Business Case Framework ensures that effective evaluation of options is conducted as a project advances through planning, design, delivery, and operation. The business case supports a systematic process of identifying, quantifying, and comparing expected benefits and costs of a project in a consistent and clear manner over its lifecycle. The work combines strategic and financial perspectives with the rigour of economic cost benefit analysis, while also incorporating operational issues and challenges.
The 20 Avenue N Street Lab Party was a first for Calgary – a public engagement trial using temporary materials to transform a street into a possible complete street configuration. This document describes the steps and tools that were developed to host the 20 Avenue N ‘Street Lab Party’. This project was initiated and completed in 2016. The City of Calgary hosted a Street Lab on August 20, 2016. The 20 Avenue N street lab party involved piloting street enhancements using tactical urbanism principles: inexpensive, quick, and temporary. The opportunity was intended to allow residents to participate in the planning and execution of the improvements to determine whether the benefits and drawbacks can be more fully assessed through experiences and observed data sets as compared with more traditional engagement approaches. This project was nominated for the TAC Sustainable Urban Transportation Award.